1. Field of the Invention
The present invention relates to a semiconductor device and to a method of manufacturing the same and, more particularly, to a semiconductor device having a structure in which plugs or wirings are connected onto a metal pattern buried in a fluorine-containing insulating film and to a method of manufacturing the same.
2. Description of the Prior Art
In recent LSI, in order to achieve the higher speed of LSI, the insulating film between wirings is made of the low dielectric constant material. As such the low dielectric constant material, there is a silicon oxide film in which fluorine or carbon is contained, for example.
The step of connecting a pad to a damascene structure metal wiring formed in an interlayer insulating film containing fluorine will now be explained.
First, as shown in FIG. 1A, a first silicon nitride film 103 is formed on an insulating film 102 made of silicon oxide, etc., formed on a semiconductor substrate 101, and then a first silicon oxide fluoride (SiOF) film 104 is formed thereon.
Then, as shown in FIG. 1B, a wiring trench (recess) 105 is formed by patterning the first SiOF film 104 and the first silicon nitride film 103. In this case, the first silicon nitride film 103 is used as an etching stopper in etching the first SiOF film 104. Then, a first barrier metal film 106 made of tantalum nitride and a first copper film 107 are formed in sequence on an inner surface of the wiring trench 105 and the first SiOF film 104. Then, as shown in FIG. 1C, the first copper film 107 on the first SiOF film 104 and the first barrier metal film 106 are left only in the wiring trench 105 by polishing them by virtue of the CMP method. The first copper film 107 and the first barrier metal film 106 in the wiring trench 105 are used as a wiring 108.
Then, a surface of the wiring 108 is cleaned by the chemicals. Then, as shown in FIG. 1D, a second silicon nitride film 109 and a second SiOF film 110 are formed in sequence on the wiring 108 and the first SiOF film 104. Then, by patterning the second SiOF film 110 and the second silicon nitride film 109 in sequence, a plurality of holes 110a are formed in the lower portion of the second SiOF film 110 and also a pad trench 110b is formed on the holes 110a. 
Then, as shown in FIG. 1E, a second barrier metal layer 111 is formed on inner surfaces of a plurality of holes 110a, an inner surface of the pad trench 110b and an upper surface of the second SiOF film 110, and then a second copper film 112 is buried in the holes 110a and the pad trench 110b. Then, the second copper film 112 and the second barrier metal layer 111 are removed from an upper surface of the second SiOF film 110 by polishing them by virtue of the CMP method. Accordingly, the second copper film 112 left in the pad trench 110b is used as a pad electrode 114, and the second copper film 112 left in the holes 110a are used as plugs 113.
After this, as shown in FIG. 1F, a third silicon nitride film 112 is formed on the pad electrode 114 and the second SiOF film 110, and then a protection insulating film 116 is formed on the third silicon nitride film 112.
However, according to the above steps, as shown in FIG. 2, the plugs 113 are peeled off from the upper surface of the wiring 108 after the protection insulating film 116 is formed. In contrast, since such peeling-off of the plugs 113 is not caused when the silicon oxide film is formed in place of the first SiOF film 104, it may be supposed that fluorine contained in the first SiOF film 104 participates in the peeling-off of the plugs 113.
By the way, the event that the metal is degraded when the metal is formed on the fluorine-containing insulating film is set forth in Patent Application Publication (KOKAI) Hei 10-144793. However, since there is no recitation that the plugs are peeled off from the polished metal wiring, the technology set forth in the above Publication cannot be applied to prevent the peeling-off of the plugs from the metal wiring.
It is an object of the present invention to provide a semiconductor device capable of maintaining good connection between a metal film buried in a trench of a fluorine-containing insulating film and another metal film connected to such metal film, and a method of manufacturing the same.
According to the present invention, after the trench is formed in the fluorine-containing insulating film, then the metal film is formed in the trench and on the fluorine-containing insulating film, and then the metal film is polished to remove from the fluorine-containing insulating film but leave in the trench, the fluorine stuck onto the surface of the metal film can be reduced.
Accordingly, after the fluorine-noncontaining insulating film, e.g., the silicon nitride film, the silicon carbide film, or the silicon oxide film is formed on the metal film buried in the trench and then the metal plugs that penetrate the fluorine-noncontaining insulating film are connected to the upper surface of the metal film, the situation that the fluorine-noncontaining insulating film is never peeled off from the metal film or the metal plugs are never separated from the metal film can be eliminated. Thus, the adhesiveness between the fluorine-noncontaining insulating film and the metal film can be improved and the connection between the metal film and the metal plugs is good.
If an amount of the fluorine on the surface of the metal film buried in the trench in this manner is reduced to less than 60% of that obtained when the surface of the copper wiring is cleaned, more preferably, less than 3.9 atom %, the adhesiveness between the metal film and the metal plugs or the metal film and the overlying fluorine-noncontaining insulating film can be improved.